The present invention relates to refrigeration appliances and more particularly to an insulation system for refrigeration appliances.
In typical domestic refrigeration appliances, the appliance oftentimes has two separate compartments which are maintained at different temperatures. For example, there may be a freezer compartment which has a temperature maintained below 0.degree. C. and a fresh food compartment which is maintained at a temperature somewhat above 0.degree. C.
In many commercially available refrigeration devices a single evaporator is used with an evaporating pressure of approximately 0-2 psig. Air is circulated over the evaporator from both the freezer compartment and the refrigerator compartment. This "mixed" air flow scheme results in dehumidification of the refrigerator compartment and subsequent frost build-up on the single evaporator coil, necessitating a periodic defrost cycle to get rid of the accumulated frost.
Also, using a single evaporator to provide the cooling for two compartments which are maintained at different temperatures results in an inefficient use of the refrigeration system for the higher temperature compartment.
It is known in the art to utilize multiple evaporators in refrigeration appliances. U.S. Pat. No. 2,576,663 discloses the use of two evaporators, each for its own refrigeration compartment. The evaporators are alternately supplied with refrigerant through a control valve.
U.S Pat. No. 3,390,540 discloses the use of multiple evaporators in a refrigeration system. Each evaporator is controlled by an expansion valve and it is possible to operate more than one evaporator at a time.
U.S. Pat. No. 3,108,453 discloses a multiple evaporator refrigeration system in which the evaporators may be used independently of each other. Also a phase change material is used in connection with at least one of the evaporators.
U.S. Pat. No. 3,786,648 discloses the use of multiple evaporators for controlling the temperature in multiple compartments with the evaporators operating independently of each other.
U.S. Pat. No. 4,439,998 discloses a refrigeration apparatus having multiple evaporators with an electronically controlled valve system to deliver refrigerant to one evaporator in preference to the other, but causing the valve system to deliver refrigerant to the other evaporator after a predetermined amount of time.
U.S. Pat. No. 4,916,916 discloses the use of a phase change energy storage material in connection with a multiple evaporator refrigeration system.
It is also known in the art to provide various different insulation systems around the different refrigerator compartments, and to use vacuum insulation panels as a part of the insulation systems. U.S. Pat. No. 2,595,874 discloses the use of a moisture impervious insulation material (foamed polystyrene) to surround the freezer compartment and the use of glass wool as the remaining insulation material. One or two evaporators may be used in that refrigerator.
U.S. Pat. No. 2,633,003 discloses the use of a more efficient insulation layer to be used around the freezer compartment in a double compartment refrigeration device. Two separate evaporators are used which may be operated in series, or the freezer evaporator may be used individually.
U.S. Pat. No. 2,739,456 discloses the use of bagged insulation around the freezer compartment and unbagged insulation around the bagged insulation and in the rest of the refrigeration device. Separate evaporators are used for the freezer and fresh food compartments.
U.S. Pat. No. 2,768,046 disclose the use of vacuum insulation panels positioned around a portion of the freezer compartment to provide enhanced insulation around that compartment.